Topsoil is sold by the cubic yard in bulk and by the cubic foot in bags, so the estimate is a volume with two ways of dividing it.
Volume (cu ft) = area (sq ft) × depth (ft)
Depth in feet = depth in inches ÷ 12
Cubic yards = cu ft ÷ 27
Bags = cu ft ÷ cu ft per bag, rounded up
A 20 × 10 ft area, 4 inches deep
The area is 200 sq ft and four inches is a third of a foot. The depth in this example is arbitrary: you set your own. The planner returns 2.47 yd³ in bulk.
Worked example 20 × 10 ft area, 4 in deep
| Material | Calculated | Buy |
|---|---|---|
| Topsoil4 in deep, no allowance | 2.469 yd³ before allowance | 2.47 yd³ |
The calculation is 2.469 yd³ before allowance. The planner’s bag option for 1.5 cu ft bags shows it as 45 × 1.5 cu ft bags, so the same project is a bulk delivery or a pile of bags depending on how you buy.
This example assumes
- 1.5 cu ft bags (the planner also offers 1 and 2 cu ft, or a custom size)
- No extra allowance, the starting value for topsoil
Weight is not volume
Suppliers may quote topsoil by weight or by the yard. Weight depends on the soil and how wet it is, so the planner does not guess it. If you enter your supplier’s density, it shows an estimated weight. With a density of 1.1 tons per cubic yard, for example, the planner’s working shows ≈ 2.72 tons, estimated from your density of 1.1 tons / yd³; that density is an input, not a standard.
What changes the estimate?
- The depth you decide on, which scales everything
- Bag size, or bulk by the yard
- An allowance for settling or uneven ground, which is off by default
- Density and moisture if you convert to weight
- Whether the topsoil is going over existing soil, which changes the depth you add
Depth is the decision
How deep topsoil should go depends on the use, the existing soil and what you are planting. This guide converts a depth you have chosen into a quantity. For spreading thin layers over a lawn, see topsoil for lawn leveling.